I need to model an open storage bin that uses an 8' dia corrugated steel pipe as the outer skin.  I have started a model using a helix and am trying to generate an equation driven curve to come up with a sine wave that has an amplitude of .5" and a period of 2 2/3" to match the way spiral wound corrugated pipes are made.

I'm having trouble setting the period and making sure the start point on the curve is at intercept point so I can relation the start point and end point vertical and have a vertical line be tangent to the peaks.

I've not worked with equation driven curves this way before and can't seem to get there.  Have any of you done something like this.

Thanks for your help

Bill Markert